Tunis (AFP) - Tunisians vote Sunday in their first presidential election since the 2011 revolution that sparked the Arab Spring, a ballot set to round off an often fraught transition to democracy.Among the 27 candidates, the hot favourite is former premier Beji Caid Essebsi, an 87-year-old veteran whose anti-Islamist Nidaa Tounes party won parliamentary elections last month.Others vying for the presidency include outgoing President Moncef Marzouki, several ministers who served under former dictator Zine El Abidine Ben Ali, leftwinger Hamma Hammami, business magnate Slim Riahi and a lone woman, magistrate Kalthoum Kannou.Some 5.3 million people are eligible to cast ballots, with tens of thousands of police and troops deployed to guarantee security amid fears Islamist militants might seek to disrupt voting.In most of the country, polls open at 8:00 am (0700 GMT) and close 10 hours later.